The present invention relates generally to fastener driving tools, and particularly to such tools being powered electrically, by compressed gas, combustion or powder.
Powered fastener-driving tools, and particularly those using compressed air as an energy source, incorporate a housing enclosing a cylinder. Slidably mounted within the cylinder is a piston assembly in communication on one side with a supply chamber and a return chamber on the opposite side thereof. The piston assembly includes a piston head and a rigid driver blade that is disposed within the cylinder. A movable valve plunger is oriented above the piston head. In its at-rest position this valve plunger prevents the drive chamber from communicating to the piston assembly and allows an air flow path to atmosphere above the piston assembly. In its actuated state, the valve plunger prevents or blocks the air flow path to atmosphere and allows an air flow path to the drive chamber.
When a tool's actuation requirements have been met, the movable valve plunger opens and exposes one side of the piston assembly to a compressed gas energy source. The resulting pressure differential causes the piston and driver blade to be actuated downward to impact a positioned fastener and drive it into a workpiece. Fasteners are fed into the nosepiece from a supply assembly, such as a magazine, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
As the piston is actuated downward, it drives the air inside the cylinder through a series of vents into the return chamber increasing the pressure in this chamber. After the fastening result has taken place, the valve plunger moves back to the at-rest position, blocking the supply chamber's air flow path to the piston head and releasing the pressure above the piston head through the path to atmosphere. At this time, the pressure built in the return chamber pushes the piston assembly back up towards the top of the cylinder. The air above the piston head is forced through the valve plunger's air flow path to atmosphere.
Other fastener driving tools operate similarly in that a reciprocating driver blade drives fasteners fed to a nosepiece by a biased magazine. The power source varies, with combustion, electric and powder operated tools being well known in the art.
Pneumatic nailers and other types of powered fastener driving tools are used in construction framing, where building panels such as plywood, wallboard, roof sheathing or other construction panels are secured to framing studs with fasteners, typically nails. A fastener that is driven into a framing stud is called a “hit” or a successful fastening result. A common problem for installers is making sure that each fastening result is a “hit” to effectively secure the panel in place. Fasteners not engaging the stud represent an unsuccessful fastening result or “miss,” which is a wasted effort as well as wasted materials.
Many installers employ separate stud finders to facilitate location of the studs, which entails additional effort and inconvenience in carrying and maintaining an extra battery-powered device. Also, the installer cannot see the stud finder's readout while working, and the use of these devices slows production, so professional installers do not typically use separate stud finders. Alternatively, other installers measure the spacing of the studs from a corner or panel edge, often using a chalk line, since studs are conventionally built on 16 inch centers or some other standard depending on the geographic location.
Also, conventional fastener-driving tools are available with built in stud finders. Such devices locate the stud, but do not indicate whether the fastener was properly driven into both the panel and the supporting stud, or improperly, only into the panel. As such, the available techniques for accurately driving fasteners are not consistently accurate, and the problem of misdirected fasteners persists in the context of framing construction.